Fuel for internal combustion engines



United States Patent O 2,891,851 FUEL FOR INTERNAL COMBUSTION ENGINES No Drawing. Application July 15, 1957 I Serial No. 671,715

Claims priority, application Great Britain July .20, 1956 2 Claims. (Cl. 44-78) This invention relates to fuels for use in internal combustion engines, and especially to diesel fuels for such engines of the injector type.

Diesel fuels often suffer from the disadvantage that they cause lacquering of the injector needles of the engine, leading to interference with the injection of the fuel into the combustion chamber, which may result in uneven combustion, carbon formation and smoking. It has been thought that this problem is related to the susceptibility of the fuel to oxidation, and such may well be the case; however, the addition of conventional oxidation inhibitors to the fuel does not solve the problem. v I

A principal object of this invention is to provide improved fuels for injector type internal combustion engines, especially such hydrocarbon diesel fuels. A more particular object is to provide fuels which have a reduced tendency to cause injector needle lacquering in. such engines. Other objects will be apparent in the description of the invention. V

It has been 'well known for many years that the cetane number of diesel fuel may be improved by the addition thereto of a dihydrocarbon peroxide or hydrocarbon hydrop eroxide, such as ditertiarybutyl peroxide or cumene hydroperoxide. However in order to bring about practical results such peroxide-type cetane improvers (or ignition promoters) have tobe used in the substantial proportions of about 1 to We have now made the surprising discovery that when a diesel fuel contains a hydrocarbon peroxide in a particular concentration range, much smaller than has heretofore been contemplated, the tendency of the fuel to cause injector needle lacquering is considerably reduced and in some cases substantially eliminated, and thatthis benefit is not obtainedoutside of the particular concentration range,

The present invention thus provides a hydrocarbon diesel fuel of reduced tendency to cause injector needle lacquering containing a small concentration, at least 0.01% by weight, but less than 0.1% byweight and preferably no more than-0.05% by weight, of a hydrocarbon peroxide. Such concentrations are so low that the addition of the hydrocarbon peroxide does not raise the cetane number of the fuel to any substantial degree, that is not more than 2 or 3 numbers at the most. In accordance with customary practice, the term hydrocarbon peroxide is used herein to denote a compound or mixture of compounds having the formula R--O-OR, wherein R is a hydrocarbon radical, such as an alkyl group, an aryl group, an arylalkyl group or an alkylaryl group, and R is a hydrogen atom or a hydrocarbon radical as in the case ofR and is either the same or different from R. Thus the term hydrocarbon peroxide denotes peroxide or a mixture of such compounds of either one or both classes.

Among the preferred hydrocarbon peroxides are the dialkyl peroxides, especially di(tertiary' alkyl) peroxides, such as ditertiary butyl peroxide. These peroxidesmay be produced by the slow oxidation of an alkane con taining at least one tertiarygcarbon atom, in the presence of a hydrogen halide. Suitable alkanes which can be so oxidised are isobutane, 2-methyl butane, 2-ethy1 butane, Z-methyl pentane, 3-methyl pentane, 2,3-dimethyl butane and 2,4-dimethyl butane. Mixtures of different peroxides may be used such as may be obtained, for example, by oxidizing a mixture of isobutane and isope'ntane or a mixture of iso-octanes resulting from the dimerization of butylene and hydrogenation of the dimer or resulting from the alkylation of isobutane with butylenes. Suitable hydrocarbon fractions maybe oxidized to give this type of peroxide, for example a kerosene.

Another preferred type of peroxide is the arylalkyl hydroperoxides, such as the hydroperoxides of cumene, paracymene, ethyl benzene, para-di-isopropylbenzene and isopropyl naphthalene. The tertiary alkyl hydroperoxides, such as tertiarylbutyl or tertiaryamyl hydroper oxide, are also suitable. v i

The hydrocarbon peroxides used in accordance with the present invention should preferably be lower mo,- lecular weight peroxides, i.e., those which contain no more than 15 carbon atoms per molecule and preferably no more than .12 carbon atoms per molecule. Ditertiarybutyl peroxide and cumene hydroperoxide, having 8 and 9 carbon atoms per molecule, respectively, are the particularly preferred hydrocarbon peroxides for use, according to our invention.

The diesel fuels of the present invention may be any of the various mixtures of hydrocarbons which can" be used as diesel fuels and thus include distillate and residual fuel oils, blends of residual fuel oils With distillates, gas. oils, recycled stock from cracking operations and blends of straight run and cracked distillates. In accord ance with ASTM Designation D975 diesel fuel has a minimum flash point of F., a minimum kinematic viscosity of 1.4 centistokes at 100 F., and depending upon the particular grade a cetane number of atleast 40 (grades 1-D and 2-D) or at least 30 (grade 4-D), and a carbon residue maximum of 0.15% (grade l-D) or 0.35% (grade 2-D). Diesel fuels will generally boil over the range of from about 300 F. or 350 F. to upwards of 600 F.

- Upon exposure to air without prior inhibition against oxidative deterioration some diesel fuels, especially those containing cracked components, will develop minute concentrations of peroxides. Such concentrations are below the range contemplated in the case of our invention and the chemical nature of such naturally formed peroxides, while not necessarily deleterious at such minute concentrations, may not be suitable to obtain the advantages of the invention. Thus the objects of the invention are best achieved by the addition of the specified amounts of the suitable hydrocarbon peroxides which we have de-, scribed above. Preferably, the base hydrocarbonfuel to which these hydrocarbon peroxides are added contains essentially no naturally developed peroxides and for best results the fuel is a straight run fuel or one which is inhibited against oxidative deterioration by the addition of an effective oxidation inhibitor soon after the components thereof have been produced by fractional distillaeither a dihydrocarbon peroxide, a hydrocarbon hydrotion. Also, or alternatively, if desired, the oxidative deterioration of the fuel can be retarded by adding an oxidation inhibitor to the feed to the last distillation step or steps in which the fuel components are produced.

If desired, the diesel fuels of our invention may contain additional additives, such as oxidation inhibitors, as discussed above, for example various alkyl phenols, such as xylenols, trimethyl phenol, 2,4-dimethyl-6-tertiary butyl phenol and 4-methyl-2,6-ditertiary butyl phenol, aromatic amines, preferably secondary aromatic amines, such as N,N-dibutylphenylene diamine, diphenylamine, phenyl alpha naphthylamine, alpha alpha, alpha beta, or beta beta dinaphthylamines, amino phenols, such as benzyl para amino phenol; anti-corrosive agents, such as dicarboxylic acids having at least 16 carbon atoms, for example alkyl succinic acids; pour point reducers; viscosity or viscosity index improvers; and wear reducers, such as carbamic acid esters and allophanic acid esters.

It is possible that with some types of diesel fuels, especially unstable cracked fuels, the addition of an organic peroxide, even in the small proportions used in accordance with this invention will give rise to some sludge formation. We have found, however, that this can easily be prevented by adding a few parts per million, for example from 1 to parts per million of a metal deactivator.

Metal deactivators which can be suitably used are condensation products obtained by the reacting of ortho hydroxy aromatic aldehydes or ketones, such as 2-hydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde and 2,2-dihydroxybenzophenone, with a primary amine, particularly a polyalkylene amine, containing at least three nitrogen atoms of which at least two are primary amino nitrogen atoms such as, for example, methyl diamine, ethylene diamine, diethylene triamine, 1:10-decylene diamine, triethylene tetramine, propylene diamine, tetraethylene pentamine, N,Ndi-beta amino ethylene piperazine; or the condensation products obtained by reacting an aromatic, aliphatic, alicyclic or heterocyclic aldehyde or ketone, such as crotonaldehyde, butyraldehyde, heptaldehyde, isobutyraldehyde, methyl hexyl ketone, furfural, acetaldehyde, acetophenone, benzaldehyde, acetone, vanillin, valeraldedehyde, octyl aldehyde, cinnamaldehyde or diisobutyl ketone, with a primary amine, particularly a polyalkylene amine having at least 3 nitrogen atoms of which at least two are primary amino nitrogen atoms of the type above described. Other suitable metal deactivators are the reaction products of a hydroxylamine with an ortho hydroxy aromatic aldehyde or an ortho hydroxy aromatic ketone.

Examples of reaction products of the foregoing type are disalicylal ethylene diamine, di(2hydroxy-3-methoxybenzal)propylene diamine, furfural triethylene tetramine, benzaldehyde tetra-ethylene pentamine, disalicylal N,N dibeta amino ethyl piperazine, dihydroxy benzophenone diethylene triamine, tri-butyraldehyde triethylene tetramine, ortho hydroxybenzandoxirne and ortho hydroxy acetophenonoxime.

The following examples illustrate the invention:

Example I The base fuel was a diesel fuel comprising 50 vol. percent of a light gas oil having a boiling range of 356 to 437 F. and 50 vol. percent of a medium gas oil having a boiling range of 437 to 608 F. To this fuel was added 0.05% by weight of cumene hydroperoxide. The resulting fuel had no injector needle lacquering tendency, although the base fuel caused very severe lacquering.

Example I] To the base diesel fuel of Example I was added 0.05%

by weight of ditertiarylbutyl peroxide to give a diesel fuel having no injector needle lacquering tendency.

4 Example III To a light gas oil having a boiling range of 356 to 437 F. was added 0.01% by weight of cumene hydroperoxide to give a diesel fuel having practically no tendency to cause injector needle lacquering. The base fuel without the peroxide caused severe lacquering.

Example IV The base fuel was a mixture of light, medium and heavy gas oils having boiling ranges of 356 to 437 F., 437 to 608 F. and 464 to 698 F., respectively and caused severe injector needle lacquering when used in diesel engines. 0.05% by weight of cumene hydroperoxide was added to this base fuel to yield a diesel fuel having no injector needle lacquering tendency.

Example V To the base fuel of Example IV, there was added 0.05% by weight of ditertiary butyl peroxide to give a diesel fuel having no injector needle lacquering tendency.

Example VI To the base fuel of Example IV was added 0.035% by weight of cumene hydroperoxide and 0.0003% by weight of disalicylal ethylenediamine. The resulting diesel fuel had no tendency to form lacquer on injector needles and sufiered no discoloration or sludge formation on prolonged storage.

Example VII A diesel fuel to which is added 0.08% by weight of diethyl peroxide has a reduced injector needle lacquering tendency.

Example VIII A diesel fuel to which 0.02% by weight of the hydroperoxide of ethyl benzene has a reduced injector needle lacquering tendency.

Example IX A diesel fuel to which has been added 0.04% by weight of a mixture of peroxides obtained by oxidizing a mixture of isobutane and isopentane has a reduced injector needle lacquering tendency.

Example X A diesel fuel to which has been added 0.05 by Weight of tertiary butyl hydroperoxide has a reduced injector needle lacquering tendency.

The foregoing examples demonstrate that the small proportions of hydrocarbon peroxides are effective to inhibit lacquering of injector needles in diesel engines. It should be noted, however, that other known cetane improvers which are not hydrocarbon peroxides have no ability to prevent injector needle lacquering. Thus, when 0.05 by weight of isopropyl nitrate or carbitol nitrate was added to the base fuel of Example IV, there was no diminution of injector needle lacquering.

While it is unexpected that such low concentrations of a hydrocarbon peroxide would be effective to reduce the injector needle lacquering tendency of diesel fuels, it is even more surprising that higher concentrations, instead of being more effective, are actually not effective at all. This is shown in the following example.

Example XI A base diesel fuel containing no peroxide was tested for injector needle lacquering tendency in a Crossley diesel engine; the lacquer forming tendency was determined by inspection of the injector needle at the completion of the test. Following the same procedure, the same base fuel was tested with varying concentrations of cumene hydroperoxide and ditertiarybutyl peroxide. The results are expressed below as the percentage of the needle area covered by lacquer, a rating technique which has been found to correlate with the weight of lacquer deposited on the needles as determined by weighing the injector needles on a micro-balance before and after chemically stripping off the lacquer.

Base iuel+0.07% by weight eumene hydroperoxide 2 Base iuel+0.08% by weight cumene hydroperoxide 2 Base fuel+0.25% by weight ditertiarybutyl peroxide. 14 Base fue1+0.07 by weight ditertiarybutyl peroxide 8 We claim as our invention: 1. A diesel fuel of reduced tendency to cause injector needle lacquering containing a minor amount, at least 0.01% and not more than 0.05% by weight, of a hydrocarbon arylalkyl hydroperoxide containing no more than 15 carbon atoms per molecule.

2. A diesel fuel of reduced tendency to cause injector needle lacquering containing a minor amount, from about 0.01 to about 0.05% by weight, of cumene hydroperoxide.

References Cited in the file of this patent UNITED STATES PATENTS 1,766,501 Buerk June 24, 1930 2,472,152 Farkas June 7, 1949 2,534,309 Sheflield Dec. 19, 1950 2,655,440 Barusch et al. Oct. 13, 1953 2,785,662 Boyce Mar. 19, 1957 

1. A DIESEL FUEL OF REDUCING TENDENCY TO CAUSE INJECTOR NEEDLE LACQUERING CONTAINING A MIN OR AMOUNT, AT LEAST 0.01% AND NOT MORE THAN 0.05% BY WEIGHT, OF A HYDROCARBON ARYLALKYL HYDROPEROXIDE CONTAINING NO MORE THAN 1K CARBON ATOMS PER MOLLECULE. 